This invention generally relates to supportive endoluminal grafts which have the ability to be delivered transluminally and expanded in place to provide a graft that is endoluminally positioned and placed, with the aid of an appropriate catheter, and that remains so placed in order to both repair a vessel defect and provide lasting support at the location of the graft. More particularly, the graft combines into a single structure both an expandable luminal prosthesis tubular support component and an elastomeric graft component wherein the material of the graft substantially covers either the internal, the external or both of the internal and external surfaces of the expandable tubular support component. When desired, the expandable supportive luminal graft takes on a bifurcated structure for repair and support of vessel locations at or near branching sites. The graft component is stretchable or elastomeric and does not substantially inhibit expansion of the tubular support component while simultaneously exhibiting porosity which facilitates normal cellular growth or invasion thereinto of tissue from the body passageway after implantation.
Elastomeric vascular grafts are known to be made by various methods. Included are methods which incorporate electrostatic spinning technology such as that described by Annis et al. in "An Elastomeric Vascular Prosthesis", Trans. Am. Soc. Artif. Intern. Organs, Vol. XXIV, pages 209-214 (1978) and in U.S. Pat. No. 4,323,525. Other approaches include elution of particulate material from tubular sheeting, such as by incorporating salts, sugars, proteins, water-soluble hydrogels, such as polyvinyl pyrrolidone, polyvinyl alcohol, and the like, within polymers and then eluting the particulate materials by immersion in water or other solvent, thereby forming pores within the polymer. Exemplary in this regard is U.S. Pat. No. 4,459,252, incorporated by reference hereinto. Another approach involves the forming of pores in polymers by phase inversion techniques wherein a solventized polymer is immersed in another solvent and the polymer coagulates while the polymer solvent is removed. Also known are spinning techniques such as those described in U.S. Pat. No. 4,475,972. By that approach, a polymer such as a polyurethane in solution is extruded as fibers from a spinnerette onto a rotating mandrel. The spinnerette system reciprocates along a path which is generally parallel to the longitudinal axis of the mandrel and at a controlled pitch angle. The result is a non-woven structure where each fiber layer is bound to the underlying fiber layer.
Also known are stent devices, which are placed or implanted within a blood vessel or other body cavity or vessel for treating occlusions, stenoses, aneurysms, disease, damage or the like within the vessel. These stents are implanted within the vascular system or other system or body vessel to reinforce collapsing, partially occluded, weakened, diseased, damaged or abnormally dilated sections of the vessel. At times, stents are used to treat disease at or near a branch, bifurcation and/or anastomosis. This runs the risk of compromising the degree of patency of the primary vessel and/or its branches or bifurcation, which may occur as a result of several problems such as displacing diseased tissue, vessel spasm, dissection with or without intimal flaps, thrombosis and embolism.
One common procedure for implanting a stent is to first open the region of the vessel with a balloon catheter and then place the stent in a position that bridges the diseased portion of the vessel. Various constructions and designs of stents are known. U.S. Pat. No. 4,140,126 describes a technique for positioning an elongated cylindrical stent at a region of an aneurysm to avoid catastrophic failure of the blood vessel wall, the stent being a cylinder that expands to an implanted configuration after insertion with the aid of a catheter. Other such devices are illustrated in U.S. Pat. No. 4,787,899 and U.S. Pat. No. 5,104,399. U.S. Pat. No. 4,503,569 and U.S. Pat. No. 4,512,338 show spring stents which expand to an implanted configuration with a change in temperature. It is implanted in a coiled configuration and then heated in place to cause the material of the spring to expand. Spring-into-place stents are shown in U.S. Pat. No. 4,580,568. U.S. Pat. No. 4,733,665 shows a number of stent configurations for implantation with the aid of a balloon catheter. U.S. Pat. No. 5,019,090 shows a generally cylindrical stent formed from a wire that is bent into a series of tight turns and then spirally wound about a cylindrical mandrel to form the stent. When radially outwardly directed forces are applied to the stent, such as by the balloon of an angioplasty catheter, the sharp bends open up and the stent diameter enlarges. U.S. Pat. No. 4,994,071 describes a bifurcating stent having a plurality of wire loops that are interconnected by an elongated wire backbone and/or by wire connections and half hitches.
Stents themselves often do not encourage normal cellular invasion and can lead to undisciplined development of cells in the stent mesh, with rapid development of cellular hyperplasia. Grafts alone do not provide adequate support in certain instances. Copending application of Jean-Pierre Dereume, Ser. No. 112,774, entitled "Luminal Graft Endoprostheses and Manufacture Thereof" describes grafts that have the ability to carry out dilatation and/or support functions. An expandable tubular support component and an elastomeric graft component are combined into a single device wherein the graft material is secured to either or both of the internal and external surfaces of the expandable support component. The graft material is produced by a spinning technique such as that described in U.S. Pat. No. 4,475,972. Also, luminal endoprostheses with an expandable coating on the surface of external walls of radially expandable tubular supports are proposed in U.S. Pat. No. 4,739,762 and U.S. Pat. No. 4,776,337. In these two patents, the coating is made from thin elastic polyurethane, Teflon film or a film of an inert biocompatible material. A. Balko et al., "Transfemoral Placement of Intraluminal Polyurethane Prosthesis for Abdominal Aortic Aneurysm", Journal of Surgical Research, 40, 305-309, 1986, and U.S. Pat. No. 5,019,090 and U.S. Pat. No. 5,092,877 mention the possibility to coat stent materials with porous or textured surfaces for cellular ingrowth or with non-thrombogenic agents and/or drugs.
By the present invention, grafts which are expandable and supportive are provided that expand from a first diameter to a second diameter which is greater than the first. When it is at its first diameter, the expandable supportive graft is of a size and shape suitable for insertion into the desired body passageway. The material of the graft is substantially inert and has a generally cylindrical cover and/or lining generally over the outside and/or inside surface of the expandable supportive component. The cover and/or lining is especially advantageous because it is elastomeric and porous to encourage desirable growth of tissue thereinto in order to assist in non-rejecting securement into place and avoidance of stenosis development. When a bifurcated expandable supportive luminal graft is desired, the porous, elastomeric liner and/or cover is secured over a bifurcated expandable understructure. The material must be elastomeric enough to allow for expansion by up to about 2 to 4 times or more of its unexpanded diameter.
It is a general object of the present invention to provide an improved luminal graft that is expandable in place and, once expanded, is self-supporting.
Another object of this invention is to provide biocompatible grafts that are expandable in vivo and are supportive once so expanded.
Another object of the present invention is to provide an improved expandable reinforced graft that is delivered by way of a balloon catheter or similar device, whether in tubular or bifurcated form, which facilitates good tissue ingrowth.
Another object of this invention is to provide an improved endoluminal graft which fully covers diseased or damaged areas for carrying out luminal repairs or treatments.
Another object of the present invention is to provide an improved endoluminal graft wherein the endoprosthesis is substantially enclosed within biocompatible elastomeric material which is presented to the surrounding tissue and blood or other body fluid.
Another object of this invention is to provide an expandable, supportive graft that can be tailored to meet a variety of needs, including a single graft designed to address more than a single objective.
Another object of the present invention is to provide a self-expanding reinforced graft that is delivered in its elongated and compressed state from within a tubular member and deployed by moving same out of the tubular member.
These and other objects, features and advantages of this invention will be clearly understood through a consideration of the following detailed description.